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Antimicrobial therapy MUDr. Lenka Černohorská, Ph.D Antimicrobial therapy MUDr. Lenka Černohorská, Ph.D. Antibiotics are substances against bacteria Other.

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Presentation on theme: "Antimicrobial therapy MUDr. Lenka Černohorská, Ph.D Antimicrobial therapy MUDr. Lenka Černohorská, Ph.D. Antibiotics are substances against bacteria Other."— Presentation transcript:

1 Antimicrobial therapy MUDr. Lenka Černohorská, Ph.D Antimicrobial therapy MUDr. Lenka Černohorská, Ph.D. Antibiotics are substances against bacteria Other groups: Antivirotics – against viruses Antituberculotics - against mycobacteria Antiparasitics – against parasites

2 Antibiotics are devided due to mechanism of efficacy into 4 groups: 1. Inhibition of cell wall synthesis (betalactames, glycopeptides) 2. Cell membrane destroy (polypeptides) 3. Inhibition of NA syntesis (quinolons, imidazols) 4. Inhibition of proteosyntesis (tetracyclines, chloramphenicol, macrolides, lincosamides, aminoglycosides) Attack against bacterial metabolism (sulfonamids)

3 Betalactames Baktericidal, only for growing bacteria Often causes allergy Penicillins (PNC, oxacillin, ampicillin, piperacillin) Cefalosporines (1.- 4. generation) Monobactams (aztreonam) Carbapenems (imipenem, meropenem)

4 Glycopeptides Reserved for G+ bacteria Vancomycin and less toxic, but more expensive teicoplaninPolypeptides Ototoxic and nefrotoxic Polymyxin B only local as part of ear drops - Otosporin Polymyxin E – colistin rare used Primary resistence: all G+ bacteria, proteus, providencia, morganella, serratia etc. 

5 Aminoglycosides Bactericidal, ototoxicity and nefrotoxicity Synergy with betalactames – decrease of toxicity Preparates: Streptomycin only against tuberculosis, gentamicin, netilmicin, amikacin, neomycin with bacitracin = framykoin (neomycin is too toxic, only for local using)

6 Tetracyklines Broad spectrum Don‘t use until 10 years (teeth development) Less used Chloramphenico l Broad spectrum Good penetration to liquor, Hematotoxicity

7 Macrolides I. generation: erythromycin, rare used II. generation: roxithromycin III. generation: clarithromycin, azithromycin – good intracellular penetration and longlasting effect, for G+ bacteriaLincosamides Lincomycin and clindamycin Reserved for surgery, good effect to G+ bacteria and anaerobes in addition to Clostridium difficile – risc of pseudomembranous enterocolitis

8 Quinolones Bactericidal Don‘t use until 15 years (growth cartilages) I. generation (oxolin acid), II. generation (norfloxacin) only for urinary infection III. generation: ofloxacin, ciprofloxacin – also for systemic infection – often used „

9 Analogs of folate acid Sulfametoxazol in combination with trimetoprim form co-trimoxazol known as BISEPTOL Bacteriostatic, worse penetrate into tissues Nitrofurantoin (and nifuratel) Effectivity on sugar metabolism. Bacteriostatic, broad spectrum For urinary tract infection. Weighty undesirable effect: GIT disorder etc. Other antibiotics Linezolid (zyvoxid) – against resistant staphylococci

10 Nitroimidazols For anaerobes, for protozoas (T. vaginalis etc.) Metronidazol, OrnidazolAntituberculotics HRZS,HRZE - starting therapy (INH, rifampicin, pyrazinamid, streptomycin, etambutol) + other HRZ,HRE – sequenced therapy

11 Antivirotics Against herpes – acyclovir… CMV – gancyklovir, foscarnet Influenza – amantadin, rimantadin, tamiflu Antiretrovirus therapy – inhibitors of reverse transcriptase (nucleosid+nonucleosid), inhibitors of protease – in combination Preparates: zidovudin, didanosin …

12 Antimycotics Fluconazol, itraconazol, ketoconazol etc. – local (vaginal, skin infection) Amphotericin B – i.v. (in sepsis) Antiparasitics Against protozoa, helmintes, ectoparasites (moore in parasite capitol) Other preparates Antimalaric: primachin, chlorochin, meflochin… Leprosity: dapson

13 Disc diffusion test MH agar is inoculated with suspension of bacteria Antibiotic discs (paper impregnated with antibiotics) are applied at MH – atb diffuse from disc through agar Concentration of atb decrease with distance from disc If microb grow to disc/if there is little zone - is resistant (not susceptible) Big zone (higher than defined size) means susceptibility.

14 Susceptibility testing in vitro The effect of therapy does not correspond with susceptibility testing in many cases Quantitative tests (MIC, E-tests) – in relevant patients Qualitative tests (disc diffusion method) – enough for common cases (susceptible - resistant)

15 Disc diffusion test MH medium inoculated with bacteria + via dispensor aplied 6 papers impregnated with antibiotics Cultivation + (37°C/18-24h) ATB diffuses from paper R s R Interpretation: High zone= susceptible bacteria (S) Small/Any zone=resistant bacteria (R)

16 Microdilution test (MIC) MIC is the lowest concentration, which inhibites growth (first clear row) On paper stencil is asigned breakpoint. If MIC is lower than breakpoint, bacteria is susceptible. If MIC is higher, bacteria will be resistent 1 plastic plate is used for 1 bacteria, for 12 antibiotics, in 8 various (decreasing) concentration (12th only in 7, because corner row upper right is growth control)

17 MIC – Material and methods bacterial suspension (0,5-1 CFU) inoculation of plate with pipette microtiter plate with 96 rows cultivation (37°C/18-24h) reading 1 row is a growth control

18 Interpretation Case -susceptible Case - resistant 4

19 PENAMSCXTCLICMPMTRPENAMSCXTCLICMPMTR 4641283264 4 1283264KR 232641632 2 641632 11632816 1 32816 0.58164880.5816488 0.2548244 48244 0.12524122 24122 0.063120.5110.063120.511 0.0310.510.250.5 0.0310.510.250.5 Interpretation of MIC - antibiogram – goes to clinician! PEN (penicillin)….4……resistant AMS (unasyn)……2…..susceptible

20 E-tests (quantitative) Similar to disc diffusion test, but strip is used An increasing concentration of atb is used. Zone is egg like. There is a scale on strip – simply reading MIC value is 0,75 mg/l (where borderline of zone cross the scale)

21 Resistance of microbes to antibiotics Primary resistance: all strains of bacteria are resistent. Secondary resistance: arises unsensitive mutants, by selective antibiotics pressure became dominant * MBC (minimum bactericidal concentracion) is the lowest concentration, which kills bacteria Primary bactericid: atb, where MIC and MBC are almost equal Primary bacteriostatic: atb, where MBC is X-fold higher than MIC - unreal baktericidal effect in human body

22 Resistance factors detection Special detection methods for resistance factors (for ex. betalactamase). It can be diagnostic strips (chemical detection of specific ensym) or other tests (ESBL) 1. Betalactamase testing In neisseria, M. catarrhalis, H. influenzae destroys betalactams For therapy we use ATB with inhibitors of betalactamase like clavulanate, sulbactam…

23 Detection of betalactamase Paper with substrate + moisturing solution Petri dish with bacteria Touch Colour change (red) After 30 sec red is missing Reaction end (yellow) Strain produces betalactamase

24 2. ESBL (extended spectrum betalactamase) E. coli, K. pneumoniae etc. produces ESBL, which destroys cheap betalactams. For therapy we use expensive carbapenems, aminoglycosides (toxicity), problem of ICU, big hospitals ESBL – screening Inhibition of growth between discs – owing to a synergism of 2-3 antibiotics such as aztreonam, AMC, ceftriaxon Amoxicilin/clavulanate aztreonam

25 ESBL detection (CLSI) 4 discs: Cefotaxim (1) and ceftazidim (2), cefotaxim with clavulanate (3) and ceftazidim with clavulanate (4) Difference between cefalosporines (1,2) and cefalosporines with clavulanate (3,4) is higher than 5mm 1 2 3 4 Compare 1 with 3 and 2 with 4

26 ESBL and AmpC detection set (A,B,C,D) Susceptible strain AmpC+ ESBL+,AMPC+ ESBL+ ABB B B A A A D CDC C D DC A cefpodoxime (CPD) B CPD+ESBL inhibitor C CPD+AmpC inhibitor D CPD+both inhibitors Interpretation: compare inhibition zones, if differences are higher than 5 mm

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